* xmlschemastypes.c: Added creation of the content type of
  xs:anyType. This is needed when trying to extend xs:anyType
  (although it makes no sense to extend it; IMHO the schema
  people should have ruled this out). This was reported
  by Yong Chen to the mailing list.
* xmlschemas.c: Fixed handling of xs:anyType in
  xmlSchemaCheckCOSCTExtends() (reported by Young Chen). Tiny
  adjustment to an error report output.
* test/schemas/extension2* result/schemas/extension2*:
  Added a test case provided by Young Chen.